I'm a neurosurgeon, which I knew was my calling long before I applied to medical school. I'm not sure what it was - my fascination with the brain or love of a challenge - but I was never going to do anything else. I always found the phrase, "It's not brain surgery," to be something of a siren call.

Of course, things got interesting when the blissful ignorance of the brash 18-year-old me collided with the realities of taking the MCATs, being accepted to and excelling in medical school, and undertaking an arduous residency.

To call neurosurgery residency long would be an understatement. It is the longest residency of any sub-specialty and, including medical school, more than one-third of my entire life has been spent at New York-Presbyterian Hospital/Columbia University Medical Center.

So much has transpired since I embarked on this long journey: I met and married my wife, I had a son, I missed my 10-year college reunion and, as of a few days ago, I completed residency and officially became a neurosurgeon.

While ancient civilizations believed that the heart or the liver was the seat of a person's soul, it is clear to me that the brain is king in this regard.

It takes a certain amount of hubris to operate on the organ responsible for a person's knowledge, memories, motor skills and ability to breathe. While I think part of this audacity is ingrained - just like my proclamation at 18 years old that I would be a neurosurgeon - much of it is learned through years of rigorous training. I am privileged to have trained with some of the best surgeons in the world.

I fondly remember the filming of the first season of "NY Med" several years ago and I think I even made it into the background of one scene. So, when I was asked if a cameraman could follow me for the second season, I gladly accepted. The crew was full of consummate professionals and created a comfortable atmosphere that I hope will help showcase my personality, as well as the rewarding and difficult realities of being a neurosurgeon.

I hope I've done my 18-year-old self proud.

Brad E. Zacharia, M.D., is a neurosurgeon at New York-Presbyterian Hospital/Columbia University Medical Center. He received his medical degree from Columbia University College of Physicians and Surgeons and has been in practice for seven years. Zacharia now appears on ABC News' "NY Med."